Electronics have been incorporated into many portable devices such as computers, mobile phones, tracking systems, scanners, etc. One drawback to portable devices is the need to include the power supply with the device. Portable devices typically use batteries as power supplies. Batteries must have sufficient capacity to power the device for at least the length of time the device is in use. Sufficient battery capacity can result in a power supply that is quite heavy or large compared to the rest of the device. Accordingly, smaller and lighter batteries (i.e., power supplies) with sufficient energy storage are desired. Other energy storage devices, such as supercapacitors, and energy conversion devices, such as photovoltaic cells and fuel cells, are alternatives to batteries for use as power supplies in portable electronics and non-portable electrical applications.
Another drawback of conventional batteries is the fact that some are fabricated from potentially toxic materials that may leak and be subject to governmental regulation. Accordingly, it is desired to provide an electrical power source that is safe, solid-state and rechargeable over many charge/discharge life cycles.
One type of an energy-storage device is a solid-state, thin-film battery. Examples of thin-film batteries are described in U.S. Pat. Nos. 5,314,765; 5,338,625; 5,445,126; 5,445,906; 5,512,147; 5,561,004; 5,567,210; 5,569,520; 5,597,660; 5,612,152; 5,654,084; and 5,705,293, each of which is herein incorporated by reference. U.S. Pat. No. 5,338,625 describes a thin-film battery, especially a thin-film microbattery, and a method for making same having application as a backup or first integrated power source for electronic devices. U.S. Pat. No. 5,445,906 describes a method and system for manufacturing a thin-film battery structure formed with the method that utilizes a plurality of deposition stations at which thin battery component films are built up in sequence upon a web-like substrate as the substrate is automatically moved through the stations.
FIG. 1A shows a prior art thin-film battery 20 formed on substrate 22. The battery includes a cathode current collector 32 and an anode current collector 34 formed on the substrate 22. A cathode layer 38 is formed on the cathode current collector 32. An electrolyte layer 42 is formed on the cathode layer 38. An anode layer 44 is formed on the electrolyte layer 42, the substrate 22 and the anode current collector 34. The current collectors 32 and 34 are connected to external circuitry to provide electrical power to the same. In a discharge operation, ions in the anode layer 44 travel through the electrolyte layer 42 and are stored in the cathode layer 38. Thereby, creating current flowing from the anode current collector 34 to the cathode current collector 32. In a charge operation, an external electrical charge is applied to the current collectors 32 and 34. Thereby, ions in the cathode layer 38 are forced through the electrolyte layer 42 and are stored in the anode layer 44.
FIG. 2A shows a prior art method for fabricating the thin-film battery 20. First, the substrate is prepared for deposition of the thin-film battery (step 215). The cathode current collector is deposited on the substrate using DC-magnetron sputtering (step 217). The cathode is deposited on the cathode current collector by RF-magnetron sputtering (step 219). In this method, the magnetron source provides sputtered material having energy of about 1 to 3 eV, which is insufficient to crystallize the cathode material to form desirable crystal structures that encourage ion movement into and out of the cathode material. The cathode must be annealed to produce a crystalline lattice structure in the cathode, which is necessary to produce an energy-storage device that has the required electrical performance characteristics. In some embodiments, a desired electrical characteristic of a battery is a discharge curve that has a relatively constant voltage (small delta) over a range of capacity and then the voltage decreases rapidly as remaining capacity is exhausted (large delta). Accordingly, the stack of the substrate, cathode current collector and the cathode are annealed at a temperature of 700 degrees Celsius (step 221 of FIG. 2A). The anneal step 221 complicates and adds cost to the fabrication of this type of solid-state battery. Further, the anneal step 221 precludes the use of any material as the substrate or other part of the battery thus formed that is unable to withstand the high anneal temperature. The anode current collector is deposited on the substrate by DC-magnetron sputtering (step 223). The electrolyte layer is deposited by RF-magnetron sputtering (step 225). The anode is deposited by thermal evaporation (step 227).
A conventional battery-powered device typically has the battery fabricated as a separate unit and then assembled to the rest of the device. Conventional batteries typically have an expected lifetime that is shorter than the rest of the device. The batteries have manufacturing steps that are incompatible with the rest of the device, or the batteries are not compatible with the manufacturing steps need for the rest of the device. Thus, it is conventionally expedient to fabricate the batteries and the rest of the device using separate manufacturing steps that do not affect the other part, and then later to unite the parts into the whole device.
Battery-powered devices are widespread and include, for example, flashlights, cordless drills and other electric-powered mechanical tools, laptop computers, CD players, MP3 players, pagers, personal data assistant devices (PDAs), radios, automobiles (whether the type that uses a battery to power the starter motor and lights, etc., or the type that uses batteries to power a main electric motor or electric-hybrid motor system), hearing aids, pacemakers, implantable drug pumps, identification tags for warehouse tracking and retail theft prevention, smart cards used for financial transactions, global positioning satellite location-determining devices, remote controllers for televisions and stereo systems, motion detectors and other sensors for security systems, talking and singing greeting cards, and many other devices.
What is needed is a long-lasting, high-reliability, low-cost, low-volume, light-weight, conformable, and/or rechargeable battery system of a desired shape that is integrated with some or all of the rest of a device.